Compound engine



(No Model.) 2 Sheets-Sheet 2,

H. DFDUQNBAR.

Compound. Engine. No. 240,239. Patented April 19,1881.

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NITED STATES Erica.

PATENT COMPOUND ENGINE.

SPECIFICATION forming part of .Letters Patent No. 240,239, dated April 19, 1881.

v Application filed January 19, 1881. (No model.)

To all whom it may concern Be it known that 1,.HENRY D. DUNBAR, of North Hartland, in the county of Windsor and State of Vermont, have invented a new and useful Improved Compound Engine, of which the following is a specification.

The object of my invention is to provide two cylinders for an engine, together with a common steam-chest, and all so provided with ports and valves that both cylinders may be used at the same time, and the pistons therein be moved by live steam, or one of said cylinders (which, for the purposes of this explanation, I will denominate the first cylinder) may be used, and the piston therein he moved by live steam, while the piston in the other or second cylinder shall only be operated upon by the exhaust-steam escaping from the first cylinder, both said pistons being secured to a rod common to both; and I accomplish this by the mechanism hereinafter described, and illustrated in the accompanying drawings, in which- Figure I is a side view of my invention. Fig. II is a plan view of the same. a Vertical longitudinal section, at line 25, of a portion of both cylinders and the steam-chest, through the ports or passages connecting the steam-chest with the cylinders, showing, more particularly, the port leading from the upper chamber of the steam-chest into the distant end of the first cylinder, A. Fig. IV is a vertical longitudinal section, at line 28, through the main ports leading from the steam-chest to the cylinders. Fig. Visahorizontalsection of the steam-chest, at line L of Fig. IV, showing a plan view of the valve-seat and valves in the upper chamber of the steam-chest. Fig. VI is a plan view of the valve-seat in the upper chamber, but with the valves removed.

In the drawings, Arepresents the large cylinder, which, for the purposes of this description, I will call the second cylinder, and A the small or first cylinder, the axes of both being coincident with a piston-rod, G, common to both, and pistons B and B, secured to said rod, each adapted to properly fill, move in, and occupy the same relative position in its respective cylinder.

A steam-chest, G, occupies the position of the ordinary steam-chest, above the cylinder,

Fig. III is but is made in two compartments or chambers, E and F, with a horizontal partition, D, dividing them, the top of said partition D forming the valve-seat of the upper chamber, E. This valve-seat is provided with the ports 1 and 5, and a casting, I, is connected with the steamchest at one end and with the cylinder A at the other end, and this casting is cored out, and is divided longitudinally inside, forming two passage-ways therein, and the valve-seat or partition D is also cored out in connection with each port 4 and 5, so that one of the passage-ways in the casting I forms the continuation of the port 4, for communication between the chamber E and one end of the first cylinder, A, and the other passage-way in said casting I forms a continuation of the port 5, for

communication between said chamber E and the other end of the cylinder, these ports opening into said cylinder, one each side the piston B. The same valve-seat is also provided with a port, 12, extending down through the partition D, and communicating with the lower chamber, F, and is also provided with exhaustports 6 and 16, which are cored outin the partition D, so as to communicate with each other, and also with an exhaust-port, 15, in the valveseat, and leading out of the chambcrE through the exhaust orifice or pipe 14.

The upper chamber, E, is provided with two slide-valves, 7 and 11, made in the ordinary manner of slide-valves, and each provided with the exhaust-cavity on its lower-face, andmoved by a valve-rod, 9, to cover or open and close the ports 4, 5, and 6 in the ordinary manner. The valve 11 is also a common slide-valve, and provided with an exhaustcavity on its lower side; and this valve is made of such a length that whenin the position shown in Fig. V its exhaust-cavity beneath communicates with the two ports 15 and 16, and when moved over into its opposite extreme position its exhaustcavity communicates with the two ports 12 and 16, and it may be moved into either position by the valve-stem 20, if on a locomotive, by the engineer in the cab.

The lower chamber, F, in the steam-chestis provided with an ordinary slide-valve, 8, adapted to slide to and fro on its valve-seat, the latter having the two ordinary ports, .1 and 2, the port 1 leading to the same end of the large cylinder A as the port 4 leads to in the small cylinder A, and the port 2 leads to the opposite end of the large cylinder A, and the exhaust-port 3 leads out through the exhaust-aperture 17.

The valve 7 in the upper chamber, E, has a rod, 9, and the valve 8 in the lower chamber, F, has a rod, 9, also, and both said rods are attached to the same valve-rocker, so that both valves are moved exactly alike and to the same extent by the same rocker. I

To prevent the steam from escaping from the small cylinder into the large one around the piston-rod G, I pack the latter at the aperture through which it passes in any desired manner.

The springs 22 are secured to the rings in difi'erent relative positions with the hole 21. If four rings are used, one spring may be secured on the same side in which the hole is made, another about one-fourth the distance around, another about half-way around, and a fourth about three-fourths the distance. After the piston-rod has been packed a cap or piece, 18, may be placed over or against the rings and the cylinder A bolted in place on the cylinder A, the piston B secured to the rod, (the piston B being secured to the same rod when preparing the cylinder A,) and the outer head to the cylinder A secured in place.

As thus arranged and in use upon a locomotive, if the valves 7 and Sin the chambers E and F are in the position shown in Fig. 1V and the valve '11 in the upper chamber, E, is in the position shown in Fig. V, if live steam is admitted to the upper chamber, E, through the orifice 13, it passes into the port at, and thence through the said port into the distant end of the small cylinder A, and exerts its force against the piston B to start it back. The live steam in the upper chamber, E, also passes down through the port 12 into the lower chamber, F, and thence down through the port 1 into the end of the large cylinder A nearest the small cylinder, and exerts its force to move the piston B in the large cylinder in the same direction that the live steam is exerting its force to move the piston B in the small cylinder at the same time, while the exhaust-steam at the other side of the piston B is free to pass out through the port 2 into the exhaust-cavity in the lower side of the valve 8, and through the exhaust-port 3, and thence out through the exhaust-orifice 17 1t will be seen that both pistons, B and B, may beoperated upon .at one and the same time by live steam admitted to both cylinders from the same steam-chest.

If it is desired to operate only one piston by live steam, the valve 11 is drawn back by its rod 20 into such a position that the exhaustcavity on its lower side covers the exhaustport 16, and also the port 12, which communi cates with the chamber below.

If the valves 7 and 8 and the pistons of both cylinders are in the same position as before,

and as shown in Fig. IV, and live steam is admitted to the upper chamber, E, of the steamchest, it will pass through the port 4 and into the distant end of the small cylinder A, but cannot pass down through the port 12 into the chamber F; but the exhaust-steam in the end of the small cylinder nearest the large one can pass out through the port 5 up into the exhaust-cavity in the lower side of the valve 7, thence down into the exhaust-port 6, and up through the exhaust-port 16 into the exhaustcavity in the lower side of the valve 11, and thence down through the port 12 into the lower chamber, F, thence through the port 1 into the large cylinder A, this exhaust-steam exerting whatever unexpended power there may be in it to force the large piston B in the same direction in which the small piston B is being forced by the live steam in the small cylinder, and the spent or exhaust steam in the large cylinder will pass out through the passage or port 2, exhaust-cavity in the lower side of the valve 8, exhaust-port 3, and orifice 17.

It will thus be seen that both pistons, B and B, may be operated by live steam at one and the same time, or one may be operated with live steam and the other with the exhauststeam escaping from the live-steam cylinder, simply by the movement of a controlling-valve by the engineer.

In cases where it is desired to use great power, when the invention is applied to a locomotivesuch as a heavy train of cars drawn up a gradethe valve 11 may be moved by the engineer from the cab, so that both pistons may be worked by the admission of live steam into both cylinders, in which case a great deal of power is gained to draw the train; but whenever it is not necessary to use so much power the valve 11 is moved by the engineer, so that the small piston B may be worked by live steam, and the other piston, B, be operated by the exhaust-steam escaping from th cylinder A.

As there is always more or less unexpended power in exhaust-steam, as practically used in a locomotive, this unexpended power is utilized in exerting force against the second piston, B, so that it becomes practical, in the use of this invention, to decrease the amount of fuel required to do the same amount of work as is now done by single engines of the same capacity by just the amount of power gained; or, in other words, with the use of this invention the same amount of work may be done as is now done in ordinary single engines of the same capacity, (engines having a single cylinder and piston of the samediameter and stroke,) with a greater economy in the use of fuel, while avery much greater gain in power is obtained without a corresponding increase in machinery by an increase in piston area, against which the steam may be made available as a workin g power.

Having thus described my invention, what I claim as new is- 1. An improved compound engine consisting of a steam-chest containing two separate and distinct; steam-chambers communicating one with the other by a port or passage-way controlled by a slide-valve, with the valve-seat in each chamber provided with the ordinary induction and exhaustports, controlledin each chamber by an ordinary slide "alve, both moved alike, two cylindeis,one of which conimunicates directly with one chamber of said steam chest, and the other cylinder with the other chamber through said induction-ports, and each cylinder containing a piston secured to the same piston-rod, whereby both said pistons may be actuated by live steam at the same time, or one may be actuated by live 

